Case Studies – Environment Management

To meet our commitment of conserving natural resources, at Roaster V at DSC, the following efforts were conceptualized and successfully implemented.

Steam is generated in WHRB during roasting operation which is used for producing power in steam turbine and steam coming out from turbine exhaust is taken directly to the condensers and in return condensate back to the WHRB without water loss. Traditionally at HZL it was done through Water Cooled Condensers at the rated capacity of 65 TPH. The water consumption in cooling towers is assumed to be of around approximately 700 M3 per day.

However, in Roaster V, first time in the history of HZL, Air cooled Condenser has been used. It saves water consumption up to 95% when compared to traditional water cooled condenser. Air cooled Condenser ( ACC ) consist of 4 modules each having 6 nos. of finned tube bundle and one CT fan and utilizes atmospheric air to condense the steam.

At all of our old smelters & Lead smelter we have commissioned the Tail Gas Treatment plants to reduce their SO2 emissions from the acid plant stack by 50% (from 4 kg/tonne to <2 kg/tonne of sulphuric acid produced). We adopted the state-of-the-art technology developed by Mitsubishi Corporation, Japan at our earlier zinc smelters to treat the gases using zinc oxide slurry and zinc sulphate solutions thus produced during the process is recycled back to the downstream for recovery of zinc.

This advanced technology was selected in preference over commonly used and cheaper technology of lime scrubbing, which produces sludge as a hazardous waste

At Lead Smelter Chanderiya Ausmelt technology is adopted. The off-gases from the Ausmelt furnace contain varying percentage of SO2 depending on the process cycle, which cannot be handled directly in acid plant due to its operational limitations. State-of-the-art technology provided by M/s Cansolv Technologies Inc.,Canada has been adopted.

This process uses the fact that SO2 is absorbed in a cold amine solution and can be easily released from the solution when the SO2 laden solution is heated. By using this process, the SO2 can be separated from the other gaseous parts of the SO2 gas. This separation of SO2 from the other gaseous compounds allows the release of the non-absorbed gases (without SO2) to the atmosphere and release of flow of concentrated SO2 gas to the sulphuric acid plant to convert these gases into sulphuric acid.

Earlier, RO rejects at DSC were being evaporated through open solar ponds and sprinkling over jarofix yard to achieve zero discharge. Now, in order to recover water from effluent streams, the RO rejects are treated through a ‘Multiple Effect Evaporator’ that effectively recovers all water in the effluent stream, leaving behind the dissolved salts.

This facility has ensured conservation of about 600 cum of water per day, thereby further improving the water recovery performance of the plant.

The dissolved salts are disposed off in secured land fills.

The waste dump, where overburden from open cast mine is stacked, causes environmental issues including fugitive dust generation through blowing wind, soil erosion due to rainfall and visual impact. To contain this, proper stabilization with vegetation/other cover is required. Growth of vegetation on barren dump is a challenge in the dry & acid climatic condition. At Rampura Agucha Mine, an innovative initiative was taken on pilot scale to cover the barren waste dump.

Use of geo-textiles / soil saver on waste dump slopes for stabilization and improved greenery: Around 12,000 sq m surface area of waste dump slope was leveled and covered by geo-textiles with vetiver plantation. Seed sowing and seed spray over the waste dump slopes: Around 1 tone of seeds has been spayed over the slopes throughout the periphery of the mine and on the stabilized slopes during the rains. A soil cover has been provided to the seeds thrown on the slopes for survival, which has resulted in good grass cover.

In 2013, we established a nursery at Rampura Agucha mines. Done to help retain the vast pool of floral species, the nursery was inaugurated on World Environment Day. Subsequently, we have launched more projects at various locations, such as:

• A floral nursery at Kayad Mine site
• A herbal nursery at Debari Zinc Smelter colony
• A seasonal nursery at Head Office, Udaipur
• A unique ‘Rashi van’ at Head Office

The objective of the In-House Nursery is conservation of biodiversity while ensuring sustained and inclusive development of the community.

HZL has constructed & commissioned Udaipur’s first STP under PPP between Government of Rajasthan. With ever increasing evidences of Climate Change impacts, especially on water sources, we have taken long strides in reducing our water foot print and also to increase the Source Water Sustainability through various PPP (Public-Private Partnership) projects with the Government of Rajasthan. One of such recent PPP project is “Installation of Municipal Sewage Treatment Plant of 20 MLD capacity in Udaipur for reduction of pollution load of the Lakes in the city and it is one of the major step towards “Swachh Bharat Mission”.

The treated water (20,000 m3/day) is being sent to Rajpura Darbia Complex of HZL through 80km long pipe line network resulting around 80% reduction in fresh water consumption of the Plant. Generated manure is being sold by Udaipur Municipal Corporation to the local bodies. With the success of phase-1 we are planning to expand this by another 40 MLD.

We made a conservation plan to conserve peacock and to increase awareness among the people of nearby village about national bird conservation. For this construction of boundary wall was made around the acquired area of 49.836 ha land and restricted the movement of people and thus providing a safe and protected environment for the endangered birds and also developing dense tree plantation of high branches that can provide shelter and habitat for the peacocks. We have also planted those species which are conducive to breeding of insects and reptiles on which the Peacocks feed. Water tanks of adequate size with water source also provided for the peacocks and other fauna species which exist in that area.

We have installed display board on the importance and methods of conservation of peacock at prominent places to increase awareness among the local population..

Managing the tailings generated at the mining operations demands constructive and channelized efforts. The post excavation activities are majorly concentrated around dealing with the tailings that cannot be recovered completely but has to be discarded scientifically to avoid any damage to the surrounding environment. The conventional trend of surface disposal of these tailings in lined pits requires huge land areas in the vicinity of the mines area.

Mining operations involve filling of stopes/voids to ensure stability and control subsidence.Mine back fill is conventionally done through hydraulic filling with cement. One of the contemporary alternative to this is the ‘Pastefill’ technology which combines the backfilling process with the tailings management. The tailings are modified into a semisolid paste which is used to fill the empty underground voids after completion of ore excavation. The paste filling process ensures fast filling of the voids with practically no bleeding.It also has other advantages of minimum water requirement and drainage;minimum fill and wall dilution in stopes,better recovery of intervening pillars;better regional stability and surface integrity.The process utilizes almost all the tailings minimizing the surface disposal. With the successful commissioning of Paste fill Plant at our Sindesar Khurd Mine and Rampura Agucha Mine, we are glad to have started a unique trend in mining in India. With both backfilling and tailings management happening simultaneously, the technology proves better than the previous low density hydraulic fill and also conserves water. Internationally we are one of those few miners who utilized tailings and operate on paste fill technology.

In our unceasing pursuit of sustainable growth, we have ventured into transforming our own Yashad (Zinc) Bhawan to earn the status of a green building. With meticulous efforts and the use of state of- the-art technologies, ’Yashad Bhawan’, Hindustan Zinc’s Head Office at Udaipur, has achieved the honor of becoming Rajasthan’s first platinum-rated green building in the existing building category, awarded by the CII-Indian Green Building Council (IGBC). Yashad Bhawan is now one of those 14 CII-IGBC buildings in India that has a platinum rating. The building was evaluated by a rigorous screening for green features under the categories of site and facility management, water efficiency, energy efficiency, and health and comfort. Some of the key green features include an integrated fresh air ventilation system, active cooling system, and air handling units (AHU) with an integrated indoor environmental quality (IEQ) monitoring system to improve indoor air quality and monitoring, online energy monitoring system, installation of water meters and creation of lush green belt across the corporate office and residential colony. Further, rooftop solar panels of 100kWp with a capacity to generate 1,62,000 units every year were installed, offsetting 15% of the total energy requirement.

The project has achieved energy savings of 27% and water use reduction of 37%. With this, Yashad Bhawan opens a novel gateway for building sustainable architecture in Rajasthan, which is known for its heritage of magnificent monuments.

The captive usage of solar energy is one of our core focus areas at Hindustan Zinc. Solar rooftop projects with a capacity of 200 KW have already been installed at each of our head offices, including the Udaipur and Chanderiya lead zinc smelter. We have commissioned 16 MW solar power projects during FY 16-17 comprising of a 12 MW project at Debari Zinc Smelter. Additionally, a solar project with a capacity of 4 MW has also been commissioned at Rajpura Dariba mine for captive consumption. Whilst the 12 MW project at Debari Zinc Smelters happens to be the largest solar energy project in the Udaipur district; the 4 MW project at Rajpura Dariba mine is the first of its kind in the Rajasmand district of Rajasthan. In the next phase, we have planned to commission a 100 MW solar power plant in near future. These efforts are geared to help Hindustan Zinc establish a firm footing in the field of solar energy generation for energy efficiency.

Cement paving blocks are precast solid products made out of cement concrete. The product is made in various sizes and shapes viz. rectangular, square, round, pentagon, I – shape etc with different dimensions with designs for interlocking of adjacent paver blocks. The conventional raw materials required for the manufacturing of paver blocks are Ordinary Portland Cement, Aggregates and Stone Dust which are available locally in every part of the country. Replacement of conventional raw materials has been validated for different grades of paver blocks from M-25 to M-40 grade. Typically 70 – 80% waste utilization was observed for the M-25 to M-30 grade paver blocks, which are preferably used for Pathways/ Pedestrian paths. More than 80,000 of M-25 grade paver blocks have been produced for internal consumption in Hindustan Zinc.